A conventional oxygen enrichment apparatus will be described with reference to FIG. 12, which provides a cross sectional view thereof. Main body 50 of the oxygen enrichment apparatus incorporates therein oxygen enriching unit 51 for increasing an oxygen concentration in the air and pump unit 53 for supplying discharge unit 52 with oxygen-enriched air obtained by oxygen enriching unit 51. Further, handle 54 for allowing a user to carry the apparatus and power cord 55 for supplying a power to pump unit 53 are also installed in main body 50. Discharge unit 52 is configured to communicate with a discharge port (not shown) provided in a headset (not shown) which is to be worn by the user on the head.
If the user wears the headset on his/her head, plugs power cord 55 in an indoor wall socket and turns on a power switch (not shown) of main body 50, the operation of pump unit 53 is initiated, whereby exterior air is suctioned into oxygen enriching unit 51 and oxygen-enriched air obtained thereby is sent to discharge unit 52, allowing the user to inhale the oxygen enriched air through the discharge port located near the user's mouth (see, for example, Japanese Utility Model No. 3096113).
Since, however, main body 50 in the conventional oxygen enrichment apparatus is operated by using an AC power, the use of the apparatus is limited only to an indoor place. That is, the apparatus could not be used outdoors or in a car where a commercial power source is not provided.
Recently, as the oxygen enrichment apparatus is gaining popularity, there is an increased demand for use for various purposes in various places: for example, use during an exercise or studying and use in an automobile. Thus, the above-mentioned spatial limitation in using the oxygen enrichment apparatus has been a problem to be solved.